1. Field of the Invention
The present invention relates to a control device for a control motor of an internal combustion engine, and more particularly to a control device for a control motor of an internal combustion engine in which the control device causes the control motor to follow a target value obtained according to an engine operational state of the internal combustion engine.
2. Description of the Related Art
Since rpm changes and load changes in a vehicle engine are great, techniques have been known which detect an operational state of the engine and control the opening and closing of a variety of control valves to achieve the optimum control in response to the operational state of the engine. For example, JP 62-126222 A describes a technique in which an exhaust control valve is provided near an open end on the downstream side of an exhaust pipe, and output increase is achieved by fully opening the control valve when the engine is in a high speed region, to utilize a dynamic effect of an exhaust system to a maximum limit on the one hand, and closing the control valve to approximately a xc2xd-opening degree to prevent the dynamic effect from operating in a reverse fashion in a medium speed region where a torque valley would be generated. A variety of proposals have also been proposed in which a control valve is provided to an interconnecting pipe connecting a plurality of intake pipes, and the control valve is caused to open and close with the engine rpm to essentially change the length of the intake pipe.
As a method in which a motor controls the control valves to follow a target opening degree, FIG. 6 illustrates one example of a method in which the target opening degree is computed based on control information, a stop target area is set around the target opening degree, and a current opening degree and the stop target area are compared against each other, to thereby control output of a motor control signal. FIG. 7 is a flow chart showing a flow of processing according to this method.
In FIG. 6, reference numeral 100 indicates a target value computing means for computing a target value of an opening degree of the control valve (hereinafter, referred to as a target opening degree), reference numeral 101 indicates control information representing an operational state of an engine which is used in the computing of the target value by the target value computing means 100, reference numeral 102 indicates a target value computed by the target value computing means 100, and reference numeral 103 indicates a stop target area which is set to a given width in which the target value is at the center of the width.
As shown in the flow chart in FIG. 7, in accordance with this method, first, a variety of sensors are used to detect the operational state of the engine which serves as control information, and, from this control information, the target value computing means 100 computes the target opening degree for the control valve that is a subject of the control (step S101). Then, the current opening degree is computed (step S102), the stop target area is set around the computed target opening degree (step S103), and the current opening degree and the stop target area are compared (step S104). Accordingly, if the current value is within the stop target area, the current value is kept (step S105), and, if the current value is outside the stop target area, a control is performed to output a motor control signal so as to bring the current value closer to the target value (step S106).
As described above, in the conventional method in which the motor is used to control the control valve so that the control valve follows the target opening degree, the target opening degree is computed based on the control information indicating the engine""s operational state. Therefore, when an operation is performed to keep uniformly the control information, in a case where the control information has a characteristic that it always fluctuates, like engine rpm for example even when the operation is performed to uniformly maintain the control information, a phenomenon may occur in which the control valve and the motor which manipulates the control valve vibrate. This phenomenon occurs in the case where there is an area where the changes in the control information cause an amount of change xcex94xcex8 in the target opening degree to be greater than the width of the stop target area. This phenomenon occurs according to the sequence shown in FIG. 8.
In FIG. 8, reference numeral 103 refers to the stop target area and reference numeral 104 refers to the current value. Portion (1) of FIG. 8 illustrates a state in which the motor current is turned off. In this state, the target opening degree fluctuates by an amount equal to xcex94xcex8. Along with this fluctuation, the stop target area 103 shifts in the forward rotational direction of the motor position by an amount equal to xcex94xcex8, and enters the state shown in portion (2) of FIG. 8. In this state, the motor current flows so as to create a forward rotation, causing the current value 104 to shift in the forward rotational direction to enter the state shown in portion (3) of FIG. 8. In this state, another fluctuation in the control information causes the target opening degree to change, this time in the opposite rotational direction from the motor position, entering the state shown in portion (4) of FIG. 8. The motor current then flows to create a reverse directional rotation, thereby entering the state shown in portion (1) of FIG. 8. The above is performed repeatedly.
As described above, the setting of the target value and fluctuation of the control information that the target value is based on, work in a joint fashion, causing a phenomenon in which the motor vibrates. This phenomenon implies that a large starting current is flown to the motor again and again. Thus, there has been a problem in that the temperature of the motor increases excessively and the longevity of the motor is reduced.
The present invention has been made to solve the above-mentioned problems, and an object of the present invention is therefore to provide a control device for a control motor of an internal combustion engine, which is capable of alleviating vibration of the control motor.
The present invention relates to a control device for controlling a control motor of an internal combustion engine which follows a target value that changes in response to an operational state of the internal combustion engine, the control device comprising: control information output means for detecting the operational state of the internal combustion engine and turning it into control information; target value computing means for obtaining the target value of the control motor corresponding to the control information outputted from the control information output means; current value detecting means for detecting a current value of the control motor; motor control signal determining means for generating a motor control signal for controlling a drive of the control motor, based on the target value and on the current value; drive means for driving the control motor based on the motor control signal; and control state information determining means for generating control state information indicating a change in the operational state of the internal combustion engine, based on a change in the control information outputted from the control information output means; in which the target value computing means corrects the control information based on the control state information, and obtains the target value corresponding to the corrected control information.
Therefore, it can be recognized that the control state information performs the manipulation such that the control information is maintained uniformly and it is possible to alleviate the phenomenon in which the motor vibrates by correcting the control information that determines the target value with the control state information.